title: One-way and reversible dual-shape effect of polymer networks based on polypentadecalactone segments.
abstract: A series of degradable polymer networks containing poly(ω-pentadecalactone) (PPD) switching segments showing a thermally-induced shape-memory effect were synthesized by co-condensation of PPD-macrotriols or -tetrols with an aliphatic diisocyanate. Thermal and mechanical properties at different temperatures were explored for polymer networks as a function of crosslink density by varying the polymer chain segment length or the netpoint functionality. All polymer networks exhibited excellent shape-memory properties with shape recovery rates Rr between 99% and 100% determined in the 5th cycle under stress-free conditions. Furthermore, the polymer networks were capable of a reversible dual-shape effect based on crystallization induced elongation (CIE) and melting-induced contraction (MIC) in cyclic, thermomechanical experiments under constant stress. In these tests, the polymer networks were capable of a shape-change of 130%. The associated temperatures at which CIE or MIC occurred (TCIE and TMIC) were shown to be a function of the applied stress. By an increase of stress of 1.6 MPa, TCIE could be increased by 10 K.
authors.affiliation: Center for Biomaterial Development and Berlin Brandenburg Center for Regenerative Therapies, Helmholtz-Zentrum Geesthacht, Teltow, Germany.
authors.forename: Marc
authors.initials: M
authors.lastname: Behl
authors.forename: Jörg
authors.initials: J
authors.lastname: Zotzmann
authors.forename: Andreas
authors.initials: A
authors.lastname: Lendlein
mesh_terms: D003432:Cross-Linking Reagents / Q000737:chemistry; D003460:Crystallization; D007783:Lactones / Q000737:chemistry*; D008956:Models, Chemical; D015394:Molecular Structure; D011091:Polyesters / Q000737:chemistry*; D013314:Stress, Mechanical; D013696:Temperature; D013718:Tensile Strength
chemical_list: D003432:Cross-Linking Reagents; D007783:Lactones; D011091:Polyesters